Steve,  I have just had the experience of making my own organ pipes
for a John Smith busker organ.  Living in a small town in Texas,
I don't have much selection for wood.  However, there are many
companies up north (mostly in Pennsylvania) that do sell quality
lumber at a very reasonable price even with the shipping, and they
will ship small orders.

I have ordered wood on several occasions and all of it was cheaper
than buying from the one and only specialty wood shop here in town.
I ordered some 2" (8/4) eastern pine and 1" maple.  With the 2" thick
stock, I was able to cut it to get quarter-sawn lumber, which has a
very nice look even in pine.  I made the mouth parts (languid, upper
and lower lip) of the pipe out of the maple.  The pipes sound great.

Mention was made of how the wood resonates and adds to the tone.  This
is true.  You should feel these little things vibrate when they play.

Okay, so I have the tools needed the cut and plane the wood.  A quality
thickness planer is really not all that expensive.  I have a very nice
Delta planer which puts on a mirror finish.  It sounds like you are
interested in working with wood.  If you can afford it, I would go
ahead and buy the proper tools because you will use them again and
again.  You can also control the thickness yourself.  If you plane
every board you are going to use at the same setting, they will all be
the same thickness, assuming your planer is set up properly.

The Baltic birch is nice, but expensive.  I used it in building the
case for the busker organ.  It's flat, doesn't warp, and stains very
nicely -- as long as you clean up the glue!  It probably would make a
nice pipe, but you would have the ply showing on the edges.  There are
not many voids in this plywood, so you could probably form a decent
edge on the languid and upper lip.  But again you are going to see the
various plies as you shape these parts.

Good luck

Jim Quashnock